I believe the whole discussion about the stall warning inhibited below 60 kts is a red herring. The stall warning on AF447 sounded continuously for 54 seconds without any indication that the crew acted on it. In my opinion it would have made no difference if it had sounded 30 seconds longer.
Once the aircraft was falling down with an airspeed less than 60 kts they probably had no way to unstall the plane anyway, they were miles away from any reasonable flight envelope for a commercial airliner, even miles away from test pilot territory. Terra incognita.
(As far as I know the stall warning is inhibited because the AoA vanes do not work below 60 kts. You cannot sound a stall warning when you have no working sensor to detect a stall.)